The present invention relates to collecting geographic data for a geographic database and more particularly, the present invention relates to a method and system for collecting road grade data for a geographic database using engine load.
Geographic databases have various uses. Geographic databases are used in in-vehicle navigation systems, personal computers, networked computing environments, and various other kinds of platforms, as well as on the Internet. Geographic databases are used with various kinds of applications to provide various navigation-related and map-related functions including map display, route calculation, route guidance, truck fleet deployment, traffic control, traffic monitoring, electronic yellow pages, roadside assistance, emergency services, and so on.
In order to provide these kinds of functions, a geographic database includes data that represent geographic features in a region. The geographic features that are represented in a geographic database may include roads, intersections, and so on. A geographic database includes information about the represented geographic features, such as the geographic coordinates of roads in a geographic region, speed limits along the road segments, locations of stop lights, turn restrictions at intersections of roads, address ranges, street names, and so on.
Collecting information for a geographic database is a significant task. Not only is the initial collection of data a significant undertaking, but a geographic database needs to be updated on a regular basis. For example, new streets are constructed, street names change, traffic signals are installed, and turn restrictions are added to existing roads. Also, new levels of detail may be added about geographic features that are already represented in an existing geographic database. For example, an existing geographic database for roads may be enhanced with information about lane widths, shoulder sizes, traffic signs, lane barriers, address ranges, sidewalks, bicycles paths, etc. Thus, there exists a need to continue to collect information for a geographic database.
One type of information that is useful to include in a geographic database is road grade information. One way of measuring road grade is with a vehicle having a mechanical road grade sensor traveling the road. Briefly, the mechanical road grade sensor has a weighted mechanical arm that gravity positions perpendicular to the horizontal plane of a vehicle when the vehicle travels on a flat road segment. When the vehicle travels on an inclined or declined road segment, gravity will position the mechanical arm at an angle to the horizontal plane of the vehicle. U.S. Pat. No. 3,752,251 illustrates an example of a mechanical road grade sensor. One shortcoming of the mechanical road grade sensors is that they may provide inaccurate road grade measurements when traveling over bumps or a rough road.
Another way of measuring road grade is with a vehicle having an altimeter, aneroid barometer or similar devices. The aneroid barometer is calibrated to show changes in atmospheric pressure in terms of linear elevation. As the vehicle travels up an incline, the aneroid barometer records the elevation at various points. The road grade may readily be determined using the elevations between the points. One shortcoming with the aneroid barometer is that it may provide inaccurate readings due to weather, wind and speed of the vehicle. Additionally, such devices are relatively expensive. Furthermore, road grade may be derived with altitude at points along the road determined using surveying equipment. However, surveying equipment may require that the equipment be mounted in a stationary position and therefore is not useable in a moving vehicle.
Accordingly, it would be beneficial to collect road grade information more inexpensively, efficiently and accurately.